Re: Black specks on image.
- View SourceHi evrybody,
Thanks for all the advice on the black specks. Concerning
the "rotation" question, I did in fact mean that when I rotated the
imager, the speck pattern stayed put within the sensor and I could
see the background moving around... indicating (not all that obvious)
that the specks were part of the sensor. Leonard, your reply was
particularly detailed and I printed it to include in my notes.
Since I was planning another Mars imaging session tonight, I got
busy putting some of the advice to use. I had already used
the "oblique high intensity light" to actually see the specks on the
cover glass, just before reading Leonard's message where he mentions
the method. It works very well. The specks really stand out, they
cant be missed. Pretty sure that was the source of the black
blotches, I carefully rubbed the glass with a dry Q-Tip. After
repeating the process 3 or 4 times and viewing the results with the
imager back in the optical track, the dozens of specks have been
reduced to one litte greyish speck in the bottom right-hand corner.
So hopefully that is what I will see when I turn on my system tonight.
While I am at it, here is some information regarding that matter
of "signal loss" from the imager which generated quite a thread some
time ago. I also had a bit of a problem with that. In the middle of
operation, the imager would suddenly go dead. Since I use a remote
viewing and control system (the telescope amd imager are outside and
I control and view from my office inside, some 60 feet distant), I
originally thought it was due to a quirky connection in the 4 USB
cables that I have linked together. Or maybe the dampness would get
to the last connection outside. When I went outside, just
disconnecting (having shut down AMCAP before) and reconnecting the
USB cables would bring back the image. But it was quite a hassle when
it occured repeatedly. The other night, however, I discovered that
just disconnecting and reconnecting the first USB cable in tne
computer did the trick just as well. So it had nothing to do with
outside conditions. I had a hunch all along that it was a software
glitch, because the signal loss always occured after an operation
such as "changing setup" in AMCAP, or "saving an image file",
or "lauching the avi file capture"... it never came just out of the
blue. So for me, disconnect and reconnect gets the signal back.
- View SourceHi again,
This is an update to the "black speck" problem. After having
cleaned the cover glass of the Neximage, I had a 4 hour imaging
session wednesday night, observing Mars magnified 1000X (Neximage and
2X barlow, with Celestron 8inch SC GPS) and making avi captures.
Finally, the image was clean, completely free of any specks! Early in
the session, there was considerable atmospheric turbulence, but this
diminished gradually to give way later on to a nice calm and humidity
free sky. I had started out making a few 500-frame captures, at
1/10sec apperture and 5 frame/sec transfer rate. I eventually
increased this to 1000, then 1500, and 2000. To close the session, I
attempted a 2500-frame capture. It was successful. Since I want to
avoid any telescope movements during a capture, Mars had to stay
within the field of view. It drifted and wandered somewhat during the
long capture, but not enough to interrupt it. I still have to process
all these images, and am quite aware of the limitations of an 8 inch
telescope with respect to resolution, however big the number of
By the way, while imaging Mars during december and perhaps
beyond, I am also reading a very interesting book on the history of
our relationship with and exploration of the planet. It is "A
traveller's guide to Mars" by William K. Hartmann, 468p, 2003.
Reading this simultaneously with the imaging makes the experience
that much more fascinating.